562 



THE BLOOD-VASCULAR SYSTEM 



Distribution of the Cerebral Arteries 



Although the brain receives its blood supply from two distinct sources, namely, from 

 the internal carotids and from the vertebrals, it is convenient to consider together the dis- 

 tribution of the various cerebral branches derived from these stems. The formation of the cir cuius 

 arteriosus (circle of Willis) and the origin of the anterior, middle and posterior cerebral arteries 

 has already been described (pp. 554, 561). The detailed distribution of these vessels will now 

 be considered. In general, their branches may be divided into central or ganglionic and per- 

 ipheral or cortical. 



The anterior cerebral artery has but a limited central distribution. It gives off a few 

 inconstant branches which enter the anterior perforated substance and supply the anterior end 

 of the caudate nucleus. One or two of these run to the corpus callosum and septum pellucidum. 

 The anterior communicating branch is a transverse trunk which connects the two arteries and 

 thereby completes the circulus arteriosus in front. It lies in front of the optic chiasm, and 

 varies considerably in length and size. It may give off some of the branches to the anterior 

 perforated substance. The cortical branches supply the gyrus rectus, the olfactory lobe and a 

 part of the orbital gyri on the ventral surface. On the medial surface branches supply the 

 cortex as far back as the parieto-occipital fissure. These branches are given off as the artery 



Fig. 459. 



-The Arteries of the Mesial Surface of the Brain. 



Sulcus cinguli Corpus callosum 



(After Spalteholz.) 



Parieto-occipital 

 fissure 



Cuneus 



Anterior cerebra' 

 artery 



Optic nerv 



Anterior communicating artery ' 

 Internal carotid artery 



Ca!carine fissure 



i Posterior cerebral artery 



Posterior communicating artery 



curves around the corpus callosum and some of them curve over onto the lateral surface and 

 supply the superior and middle temporal convolutions. Branches from the anterior cerebral 

 artery also_ supply the corpus callosum (fig. 459). 



The middle cerebral artery gives off most of the branches to the basal ganglia and supplies 

 the greater part of the lateral surface of the brain. It runs through the lateral fissure (fissure 

 of Sylvius) (fig. 460). The branches of the middle cerebral include the following: 



The central branches are: — ^(i) The caudate, two or three small branches, which arise from 

 the medial aspect of the artery and pass through the medial part of the floor of the lateral fissure 

 (fissure of Sylvius) to the head of the caudate nucleus, (ii) The antero-lateral are numerous 

 small arteries which pass through the anterior perforated substance and supply the caudate 

 nucleus (except its head), the internal capsule, and part of the optic thalamus, (iii) The 

 lenticulostriate, a larger branch of the antero-lateral set, passes through a separate aperture in 

 the lateral i)art of the anterior perforated substance, runs upward between the lenticular nucleus, 

 which it .supi)lies, and the ext('rnal capsule, perforates the internal capsule, and terminates in the 

 caudate nucleus. It has been so frequently found ruptured in apoplexy that it is called by 

 CJharcot the 'artery of cerebral haemorrhages.' (iv) Sometimes a more or less distinct branch, 

 called lenticulo-optic, is dislributeul to tlie lateral and hinder portion of the lenticular nucleus 

 and the lateral portion of tin; oi)tic tlialamus. 



The cortical branches come off opposite tlie insula. They supply the insula, the inferior 

 frontal gvri, the centr.al gyri (anterior and posterior), the parietal lobules, superior and in- 

 ferior, the supra-marginal, angular, and superior temporal gyri. 



The posterior cerebral give off both central and cortical branches. The central branches 

 are the postero-median, posterior chorioid, and the postero-lateral. The postero-median 



